Multiple ion injection in mass spectrometry

Abstract

This invention relates to mass spectrometry that includes ion trapping in at least one of the stages of mass analysis. In particular, although not exclusively, this invention relates to tandem mass spectrometry where precursor ions and fragment ions are analysed. A method of mass spectrometry is provided comprising the sequential steps of: accumulating in an ion store a sample of one type of ions to be analysed; accumulating in the ion store a sample of another type of ions to be analysed; and mass analysing the combined samples of the ions; wherein the method comprises accumulating the sample of the one type of ions and/or the sample of another type of ions to achieve a target number of ions based on the results of a previous measurement of the respective type of ions.

1. A method of mass spectrometry comprising the sequential steps of:
 accumulating in an ion store a sample of one type of ions to be analysed; 
 accumulating in the ion store a sample of another type of ions to be analysed; and 
 mass analysing the combined samples of the ions at a first mass analyser; 
 wherein the method comprises accumulating the sample of the one type of ions and/or the sample of another type of ions to achieve a target number of ions based on the results of a previous measurement of the respective type of ions, the previous measurement being performed at a second mass analyser different from the first mass analyser. 
 
     
     
       2. The method of  claim 1 , further comprising:
 for a particular type of the first and second types of ions, accumulating over a test injection time a test sample of the particular type of ions to be analysed, measuring the abundance of the particular type of ions so accumulated, and determining a target injection time that will result in a desired target abundance of the particular type of ions based upon the test injection time and the measured abundance of the particular type of ions; and wherein 
 the particular type of ions are accumulated in the ion store for the target injection time before mass analysis of the combined samples. 
 
     
     
       3. The method of  claim 2 , wherein the test sample and the particular type of ions are accumulated in different ion stores. 
     
     
       4. The method of  claim 2 , further comprising operating an ion source to generate the particular type of ions, directing the generated ions to an ion store for accumulation over the test injection time and to an ion store for accumulation over the target injection time. 
     
     
       5. The method of  claim 2 , further comprising operating an ion source to generate ions, directing the generated ions to a reaction cell where they undergo a reaction that changes the ion population to form the particular type of ions. 
     
     
       6. The method of  claim 5 , wherein the ion store forms the reaction cell. 
     
     
       7. The method of  claim 5 , wherein reacting the ions comprises fragmenting the ions and accumulating product ions in the ion store. 
     
     
       8. The method of  claim 7 , comprising selecting a precursor ion type, fragmenting those ions, and accumulating product ions in the ion store. 
     
     
       9. The method of  claim 8 , comprising selecting a plurality of precursor ion types, fragmenting those ions, and accumulating product ions in the ion store. 
     
     
       10. The method of  claim 9 , comprising varying the reaction cell conditions according to the precursor ions being fragmented. 
     
     
       11. The method of  claim 5 , further comprising directing the particular type of ions to an ion store for accumulation over the test injection time and for accumulation over the target injection time. 
     
     
       12. The method of  claim 5 , wherein the ion store provides the reaction cell, the method comprising allowing the reaction to continue for the test injection time and the target injection time thereby to accumulate the particular type of ions. 
     
     
       13. The method of  claim 4 , comprising reacting the ions with a gas phase present in a reaction cell. 
     
     
       14. The method of  claim 2 , further comprising repeating the steps of accumulating over a test injection time a test sample of the particular type of ions to be analysed, measuring the abundance of the particular type of ions so accumulated, and determining a target injection time that will result in a desired target abundance of the particular type of ions based upon the test injection time and the measured abundance of the particular type of ions for the other type of ions. 
     
     
       15. The method of  claim 14 , wherein the combined desired target abundances of the particular type and the other type of ions substantially matches the storage capacity of the ion store for the required performance. 
     
     
       16. The method of  claim 1 , comprising operating a single ion source of the mass spectrometer to generate both types of ions. 
     
     
       17. The method of  claim 1 , comprising operating a first ion source to generate one of the types of ions and subsequently operating a second ion source to generate the other of the types of ions. 
     
     
       18. The method of  claim 1 , comprising accumulating the sample of one type of ion and/or the another type of ion concurrently with mass analysing a combined set of previously accumulated ions. 
     
     
       19. The method of  claim 17 , comprising applying a first voltage to an electrode arrangement to create an electrical field to guide ions produced by the first ion source to the ion store and applying a second voltage to the electrode arrangement to create an electrical field to guide ions produced by the second ion source to the ion store. 
     
     
       20. The method of  claim 17 , comprising applying a first current to a magnet arrangement to create a magnetic field to guide ions produced by the first ion source to the ion store and applying a second current to the magnet arrangement to create a magnetic field to guide ions produced by the second ion source to the ion store. 
     
     
       21. The method of  claim 19 , wherein the switch between electrical fields is performed without movement of the electrode arrangement. 
     
     
       22. The method of  claim 1 , further comprising operating the mass spectrometer under conditions favourable to the accumulation of either type of ions. 
     
     
       23. The method of  claim 1 , comprising operating the mass spectrometer under conditions favourable to the accumulation of both types of ions during respective accumulation periods. 
     
     
       24. The method of  claim 22 , comprising operating a mass filter to select preferentially either type of ions or both types of ions, to be stored in the ion store. 
     
     
       25. The method of  claim 22 , comprising operating ion optics to transmit preferentially either type of ions or both types of ions, to the ion store. 
     
     
       26. The method of  claim 1 , wherein one of the ion types is an internal calibrant and the other ion type is a sample to be analysed. 
     
     
       27. The method of  claim 26  comprising using a single ion source to generate the internal calibrant and the sample ions together. 
     
     
       28. The method of  claim 1 , comprising reacting one of the types of ions to form an internal calibrant. 
     
     
       29. The method of  claim 1 , further comprising causing parent ions to fragment to form product ions and wherein one of the ion types corresponds to parent ions and the other ion type corresponds to product ions. 
     
     
       30. The method of  claim 1 , wherein the two type of ions have different mass ranges. 
     
     
       31. The method of  claim 30 , wherein the different mass ranges are adjacent, separated or overlapping. 
     
     
       32. The method of  claim 1 , further comprising reacting the two types of ions with each other prior to performing the mass analysis. 
     
     
       33. The method of  claim 32 , wherein the two types of ions are of opposite polarities. 
     
     
       34. The method of  claim 1 , wherein the types of ions to be accumulated are selected according to information obtained from a previously acquired mass spectrum. 
     
     
       35. The method of  claim 1 , comprising performing MS n  spectrometry. 
     
     
       36. The method of  claim 1 , comprising ejecting the combined sample of ions from the ion store to a separate mass analyser for mass analysis. 
     
     
       37. The method of  claim 36 , wherein the mass analyser is any of the following types: Fourier transform ion cyclotron resonance, multi-reflection electrostatic trap including Orbitrap, or singly- or multiply-reflecting time-of-flight. 
     
     
       38. The method of  claim 36 , wherein, after the ejection of the combined sample of ions from the ion store, ions are returned from the separate mass analyser back to the ion store.